Explanation for shrink fingers after bathing

Scientists analyze the phenomenon of wrinkled skin in the computer model

06/02/2014

Everyone knows the phenomenon of wrinkled skin after bathing, but it does pose a very difficult question to science. For a short time after staying in the water, the skin is smooth again and shows no lasting damage. The researchers around Professor Roland Roth from the Institute for Theoretical Physics of the University of Tübingen and the physicist Dr. Ing. Myfanwy Evans from the Friedrich-Alexander University Erlangen-Nuremberg (FAU) now uses a physical model to study the computer more closely and gain amazing new insights. Their results were in the trade magazine „Physical Review Letters“ released.

For the first time, scientists from the universities of Erlangen-Nuremberg and Tübingen modeled „Computer the structure of the outer skin layer on the mesoscopic scale“, to clarify why the fingers become wrinkled after a bath and how the skin then smoothes out again. „If we spend a long time in the water, our skin absorbs moisture and the cells of the outer skin layer swell up. In a dry environment, the skin releases the additionally absorbed water without lasting damage and is smooth again a short time later“, describes the University of Tübingen the phenomenon. According to the scientists, the keratin fibers of the outer skin cells play an essential role here. In their computer model, the researchers have now calculated the processes that take place in the water absorption in the individual components of the skin, and put it to their own account „an interesting interplay of forces in the outer skin cells.“

Interplay of forces in the outer skin layer
The scientists explain that keratin fibers are present in a geometrically ordered structure in the outer skin layer. The keratin is there „hydrophilic, so it feels very well in an aqueous environment“, why the skin cells absorb the water while bathing. The absorption of water results in swelling of the cells, causing the keratin fibers to stretch, the researchers write. „Like a spiral spring that you pull out“, this in turn requires elastic energy. By „the interplay of these forces acting in opposite directions“, the expansion of the cells is brought to a standstill and limits the maximum water intake of the skin, so the announcement of the University of Tübingen. In the end, stop that „Expansion, before the keratin fibers can touch and permanently crosslink, resulting in a permanent change in the mechanical properties of the cells“ or lasting damage to the skin would result. Since the fibers do not cross-link, the skin can give off the absorbed water again after bathing and smooth itself without permanent damage.

Evolutionary advantage of the wrinkled fingers remains unclear
Based on the computer model, it has become clear which processes lead to wrinkled fingers during bathing and how the skin subsequently smoothes out again. But it still remains unclear what evolutionary advantage the wrinkled skin offers or why the body has this property. So far, the discussion has been mainly about the aspect of liability or liability „brains“. Thus, some researchers assume that with wrinkled fingers objects can be better grasped or held in the water. However, younger studies could not confirm this effect. Even if they can not provide an answer to this question, the scientists of the Universities of Erlangen-Nuremberg and Tübingen hope that their computer model will help in the future, „To better understand and treat skin diseases, and to create artificial materials modeled on the skin.“ (Fp)

Picture: Günther Gumhold